1. Field of the Invention
The present invention relates to a wireless communication system having a hierarchical cell structure. More particularly, the present invention relates to an apparatus and method for improving system performance in a wireless communication system of a hierarchical cell structure.
2. Description of the Related Art
A cellular communication system provides a wireless communication system of a hierarchical cell structure where base stations having different cell coverage coexist for swift communication of a terminal. That is, the cellular communication system provides a communication system where a small cell such as a pico cell and a femto cell, and a macro cell coexist.
The wireless communication system of a hierarchical cell structure according to the related art applies the same wireless communication standard to a macro cell and a small cell, and provides various transmission techniques for providing data to a low speed user and a high speed user.
FIG. 1 illustrates a wireless communication system of a hierarchical cell structure according to the related art.
As illustrated in FIG. 1, the wireless communication system of the hierarchical cell structure may reduce a service shadow region generated in the case where only a macro base station 100 is used by allowing the macro base station 100 and a plurality of small base stations 110 and 112 to coexist, may extend a cell coverage region supportable by the macro base station 100, and may improve a data transmission rate that can be provided per area.
In the wireless communication system of the hierarchical cell structure according to the related art, a terminal receives a service from one of the macro base station 100 and a small base station 110. That is, when a first terminal 120 that receives a service from the macro base station 100 moves into the coverage region of the small base station 110, the first terminal 120 performs a handover procedure from the macro base station 100 to the small base station 110 to disconnect a connection with the macro base station 100 and try a connection to the small base station 110. However, when the first terminal 120 is moving at a high speed, since the first terminal 120 passes through the coverage region of the small base station 110 within a very short period of time, the first terminal 120 performs a handover procedure again. This frequent and unnecessary handover procedure increases the overhead of a system and reduces the performance of the system.